The present disclosure relates generally to speed-reducing gearbox assemblies for use with turbine engines and, more specifically, to systems and methods of reducing vibratory responses induced into at least one of an engine and an airframe from a gearbox assembly.
At least some known gas turbine engines, such as turbofans, include a fan, a core engine, and a power turbine. The core engine includes at least one compressor, a combustor, and a high-pressure turbine coupled together in a serial flow relationship. More specifically, the compressor and high-pressure turbine are coupled through a shaft to form a high-pressure rotor assembly. Air entering the core engine is mixed with fuel and ignited to form a high energy gas stream. The high energy gas stream flows through the high-pressure turbine to rotatably drive the high-pressure turbine such that the shaft rotatably drives the compressor. The gas stream expands as it flows through a power or low-pressure turbine positioned aft of the high-pressure turbine. The low-pressure turbine includes a rotor assembly having a fan coupled to a drive shaft. The low-pressure turbine rotatably drives the fan through the drive shaft, and turbine engine performance is enhanced when the low-pressure turbine operates at a relatively high rotational speed and when the fan operates at a relatively low rotational speed and with a low pressure ratio.
Many modern commercial turbofans are manufactured with increasingly large bypass ratios to facilitate improving engine efficiency. However, increasing the bypass ratio of the turbofan results in an increased fan size and fan tip speed, which must be controlled to maintain the efficiency of the turbofan. As such, at least some known turbofans include a speed-reducing gearbox coupled along the drive shaft between the low-pressure turbine and the fan, such that the fan rotates at a different speed than the low-pressure turbine. However, speed-reducing gearboxes generally increase the weight and the complexity of the turbofan, induce vibrations to the propulsion system or the airframe of an associated aircraft, and increase noise in a passenger cabin of the aircraft. Therefore, it is desired to have a turbofan that induces less vibration and noise to the associated aircraft.